Question

Two blocks $A$ and $B$ of masses $5kg$ and $3kg$ respectively rest on a smooth horizontal surface with $B$ over $A$. The coefficient of friction between $A$ and $B$ is $0.5$. The maximum horizontal force (in $kg$ wt.) that can be applied to $A$, so that there will be motion of $A$ and $B$ without relative slipping, is

• A. 1.5
• B. 2.5
• C. 4
• D. 5

Answer 1

Answer: (C)

It both are moving together
$a=\frac{F}{8}$
for $3kg$ block
$f=3\left(\frac{F}{8}\right)$
$(0.5(3)g=\frac{3F}{8}$
$F=40N$
$So,m=4kg$